One aspect of this invention pertains to colored, or dyed, hydrogel or silicon hydrogel substrate, and more particularly to compositions and methods for reversibly dyeing soft contact lenses.
Colored contact lenses have been steadily gaining in popularity amongst individuals who want to change their eye color or add a dramatic new feature to their appearance. Contact lens makers first started adding color to contact lens in the 1970s to make the lenses easier to see. The amount of pigment used to create this “handling tint” is so slight that it has essentially no effect on how the lens looks on the eye. By the 1980s, iris-altering contacts had been created. Some offered subtle changes, such as lenses that made blue eyes look bluer. Other, novelty lenses became available that could change the eye's appearance dramatically, such as by turning the iris a blood-red color, for instance, or making it look like a cat's eye.
The simplest colored lenses are enhancing lenses, which look like a regular contact lens with an iris-sized circle of transparent color. These lenses aren't meant to hide the iris's natural color, but rather to augment it. Manufacturers create the color by covalently attaching organic azo dyes to the contact lens polymer. The use of opaque pigments is more difficult, as it has a tendency to look fake. Colored contact makers have gotten better at making dramatic yet realistic-looking changes to the appearance of the iris through the use of sophisticated designs of opaque inorganic pigments. Nano- and microscale particles of inorganic pigments such as titanium dioxide, iron oxide, and barium sulfate are typically used to achieve the opaque color in these lenses. The FDA has only approved a small number of pigments for use with contact lenses. It is also important that the pigment used have no effect on the morphology and overall mechanical properties of the lens.
For some lenses, inks are printed directly onto the lens and then covalently fixed onto the polymer surface. Other colored contact lenses are made by putting the inks into a mold and polymerizing the lens around these pigments, encapsulating the color within the contact. Others are made by stacking layers of dielectric films of alternating low and high refractive index. This, in combination with the films' precise nanoscale thickness, allows scientists to tailor the lens's reflective properties and therefore its color. The thin films are applied to the lens using plasma-enhanced chemical vapor deposition or ion-assisted deposition. The process creates a smooth surface on the lens that's imperceptible to the wearer. All of these processes are complicated and require precise application of pigments or films through the use of highly sensitive and technical machinery.
Colored contact lenses that have a dyed iris area and a light reflecting material on the concave surface of the lens are known. The reactive dyes are attached to the lens through the formation of a covalent bond between the lens material and the dye that is created after the lens is contacted with the dye for a sufficient amount of time. These dyes permanently stain the matrix of the contact lens.
Also known are colored contact lenses in which the color is applied by direct application of one or more vat dyes, by printing the color onto the surface of the lens, or by incorporating a pigment onto the contact lens surface. These contact lenses are also permanently colored.
What is needed, therefore, is a simple method and kit for coloring contact lenses that is reversible and not permanent.